Pressure sensor

ABSTRACT

A pressure sensor using the MEMS device comprises an airtight ring surrounding a chamber defined by the first substrate and the second substrate. The airtight ring extends from the upper surface of the second substrate to the interface between the first substrate and the second substrate and further breaks out the interface. The pressure sensor utilizes the airtight ring to retain the airtightness of the chamber.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Divisional co-pending application Ser. No.14/596,967, filed on Jan. 14, 2015, for which priority is claimed under35 U.S.C. §120; and this application claims priority of Application No.103121910 filed in Taiwan on Jun. 25, 2014 under 35 U.S.C. §119, theentire contents of all of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a pressure sensor and a manufacturemethod thereof, particularly to a pressure sensor and manufacture methodthereof complied with the Microelectromechanical System (MEMS)equipment.

2. Description of the Prior Art

Since the development in 1970, the Microelectromechanical System (MEMS)equipment has been improved from subject in the laboratory research tothat for high-level system integration. The MEMS equipment also has apopular application and an amazing and stable growth in the publicconsumable field. The MEMS equipment is capable of achieving thefunctions of the equipment through detecting or controlling thekinematic physical quantity of the movable MEMS elements. For example,the pressure sensor implemented with the MEMS equipment utilizes thepressure difference between an airtight chamber and the outsideenvironment to drive the MEMS element, produce the deformation, anddetect the pressure difference from the outside environment. To sum upthe foregoing descriptions, how to preserve the airtight chamber is themost important goal of the pressure sensor implemented with the MEMSequipment.

SUMMARY OF THE INVENTION

The present invention is directed to providing a pressure sensor and amanufacture method thereof implemented with the MEMS equipment. Anairtight ring is configured for surrounding a chamber defined by a firstsubstrate and a second substrate, and the airtight ring extends from theupper surface of the second substrate comprising the MEMS device to thesurface between the first substrate and the second substrate to retainthe airtight chamber.

The pressure sensor according to one embodiment of the present inventioncomprises a first substrate and a second substrate. The first substratecomprises a metal layer, wherein the metal layer is partially exposed ona surface of the first substrate to form a first circuit, a secondcircuit and a conductive contact. The second substrate comprises a firstsurface and a second surface, wherein the second substrate faces thesurface of the first substrate with the first surface and iselectrically connected to the conductive contact. The second substratecomprises a MEMS element, corresponding to the first circuit anddefining an airtight chamber with the first substrate and the secondsubstrate; a reference element, corresponding to the second circuit andkept a fixed distance from the second circuit; and a first airtight ringconfigured surrounding the chamber, wherein the first airtight ringpenetrates the second surface of the second substrate, extends to aninterface between the first substrate and the second substrate, andprotrudes from and breaks out the interface.

Other advantages of the present invention will become apparent from thefollowing descriptions taken in conjunction with the accompanyingdrawings wherein certain embodiments of the present invention are setforth by way of illustration and examples.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing aspects and many of the accompanying advantages of thisinvention will become more readily appreciated as the same becomesbetter understood by reference to the following detailed descriptions,when taken in conjunction with the accompanying drawings, wherein:

FIG. 1 is a cross-sectional diagram showing a pressure sensor of apreferred embodiment of the present invention;

FIG. 2 is a schematic diagram showing the layout of the chamber and theairtight ring of the pressure sensor of a preferred embodiment of thepresent invention;

FIG. 3 is a cross-sectional diagram showing a pressure sensor of anotherpreferred embodiment of the present invention;

FIG. 4 is a schematic diagram showing the layout of the chamber, theairtight ring and the micro channel of the pressure sensor of apreferred embodiment of the present invention shown in FIG. 3;

FIG. 5 is a cross-sectional diagram showing a pressure sensor of thethird embodiment of the present invention;

FIG. 6 is a cross-sectional diagram showing a pressure sensor of thefourth embodiment of the present invention;

FIG. 7 is a partial schematic diagram showing the structure of the microchannel of the pressure sensor of a preferred embodiment of the presentinvention;

FIG. 8 is a partial schematic diagram showing the structure of the microchannel of the pressure sensor of a preferred embodiment of the presentinvention;

FIG. 9 is a partial cross-sectional diagram showing the structure of themicro channel of the pressure sensor of a preferred embodiment of thepresent invention;

FIGS. 10a to 10g are cross-sectional diagrams showing the manufacturesteps of the pressure sensor of a preferred embodiment of the presentinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The pressure sensor of the present invention is accomplished with themicroelectromechanical system (MEMS) equipment. Referring to FIG. 1 andFIG. 2, the pressure sensor 1 of one preferred embodiment of the presentinvention comprises a first substrate 11 and a second substrate 12. Thefirst substrate 11 comprises at least one metal layer. In the embodimentshown in FIG. 1, the first substrate 11 comprises the metal layer 111 aand 111 b, and the metal layer 111 b on the upper layer is partiallyexposed on the surface of the first substrate 11. The exposed metallayer 111 b may function as a first circuit 113 a, a second circuit 113b and a conductive contact 113 c. In one preferred embodiment, the firstsubstrate 11 is a complementary metal oxide semiconductor substrate.

The second substrate 12 comprises a first surface 121 and a secondsurface 122, and the second substrate 12 faces the surface of the firstsubstrate 11 with the first surface 121 and is electrically connected tothe conductive contact 113 c of the first substrate 11. For example, thesecond substrate 12 comprises at least one conductive via 123 bpenetrating the first surface 121 and the second surface 122 of thesecond substrate 12. The conductive via 123 b is electrically connectedto the conductive contact 113 c and the second substrate 12 through anohmic contact, wherein the ohmic contact is formed by the conductive via123 b and the second surface 122 of the second substrate 12 or the sidewall of the conductive via 123 b. In one preferred embodiment, the ohmiccontact region comprises at least one of silicon, aluminum-copper alloy,titanium nitride and tungsten.

Further, the second substrate 12 comprises a microelectromechanicalsystem (MEMS) element 124, a reference element 125 and a first airtightring 123 a. The MEMS element 124 corresponds to the first circuit 113 aof the first substrate 11 and defines an airtight chamber 126 with thefirst substrate 11 and the second substrate 12. The pressure differencebetween the inside and the outside of the chamber 126 may create adeformation of the MEMS element 124 forward or backward the firstsubstrate 11. The MEMS element 124 is electrically coupled to the firstcircuit 113 a to measure the deformation level of the MEMS element 124.The reference element 125 corresponds to the second circuit 113 b and iskept a fixed distance from the second circuit 113 b. To be simple, thereference element 125 is not deformed with the pressure difference, sothat the reference element 125 is electrically coupled to the secondcircuit 113 b to provide a stable reference signal. In One preferredembodiment, the thickness of the reference element 125 may be increasedso as to avoid the reference element 125 from being deformed with theoutside pressure difference.

The first airtight ring 123 a is configured for surrounding the chamber126. In one preferred embodiment, the shape of the first airtight ring123 a may be circular (as shown in FIG. 2), rectangle, polygon or othersuitable shape. The first airtight ring 123 a penetrates the secondsurface 122 of the second substrate 12 and extends to an interfacebetween the first substrate 11 and the second substrate 12. It should benoted here that the first airtight ring 123 a may further break out theinterface between the first substrate 11 and the second substrate 12.According to this structure, the interface between the first substrate11 and the second substrate 12 extending outward from the chamber 126 isblocked by the first airtight ring 123 a to prevent the air leakage atthe interface between the first substrate 11 and the second substrate 12caused by the unevenness of the surface of the first substrate 11 or thefirst surface 121 of the second substrate 12, or the mounting failurebetween the first substrate 11 and the second substrate 12. In apreferred embodiment, the first airtight ring 123 extends to the metallayer 111 b of the first substrate 11 and is connected to the metallayer 111 b to further improve the airtightness of the chamber 126.

In one preferred embodiment, the material of the first airtight ring 123may be the same as or different from the conductive material (such astungsten) used in the conductive via 123 b. It should be noted here thatthe conductive via 123 b and the first airtight ring 123 a may beintegrated together. For example, the first airtight ring 123 a is aconductive material, and the metal layer 111 b connecting to the firstairtight ring 123 a is a well-designed conductive contact as well, sothat the first airtight ring 123 a may be used as a conductive via andprovide an alternative conductive path of the electrical connectionbetween the first substrate 11 and the second substrate 12. Besides, theconductive via 123 b may be omitted as well.

In the embodiment shown in FIG. 1, the first substrate 11 comprisesmultiple metal layers 111 a and 111 b. For reducing the probability ofair leakage between the metal layers 111 a and 111 b of the firstsubstrate 11, a second airtight ring 118 c may be configuredcorresponding to the first airtight ring 123 a, that surrounds thechamber 126. The second airtight ring 118 c is connected to the metallayers 111 a and 111 b to improve the airtightness of the firstsubstrate 11.

Referring to FIG. 1, in one preferred embodiment, the pressure sensorfurther comprises a third substrate 13. The third substrate 13 comprisesa plurality of bracket structure 131 surrounding a notch region 132. Thethird substrate 13 is configured above the second substrate 12 and isconnected to the first substrate 11 through the bracket structure 131 toplace the second substrate 12 in the notch region 132 of the thirdsubstrate 13. In one preferred embodiment, the third substrate 13 isconductive and the contact pad 133 is provided at the terminal of thebracket structure 131. The third substrate 13 is eutectically bondedwith the first substrate 11 to make the contact pad 133 and the contactregion 113 d of the first substrate 11 forming a low-impedanceconductive contact. For example, the third substrate 13 comprises atleast one of silicon-doped ceramics having conductive plating, glasshaving Indium Tin Oxide (ITO) coating, and Tantalum oxide. The thirdsubstrate 13 also has a channel 134 connecting the notch region 132 andthe outside to make the pressure of the notch region 132 and the outsideequal. In one preferred embodiment, the channel 134 is configured on theterminal of the bracket structure 131.

Please refer to FIG. 3 and FIG. 4, in one embodiment, the firstsubstrate 11 and the second substrate 12 further define a micro channel117 extending from the chamber 126 to the first airtight ring 123 a.Therefore, in the manufacture process, the anti-sticking material may beled to the chamber 126 via the micro channel 117 before forming thefirst airtight ring 123 a and forms the anti-sticking layer on the innersurface of the chamber 126. For example, the anti-sticking material maybe the self assembled monolayer (SAM) material, such asdichlordimethylsilane (DDMS), octadecyltrichlorsilane (OTS),perfluoroctyltrichlorsilane (PFOTCS), perfluorodecyl-trichlorosilane(FDTS), or fluoroalkylsilane (FOTS). The anti-sticking layer on theinner surface of the chamber 126 may avoid the sticking between the MEMSelement 124 and the first substrate 11. Furthermore, an anti-moving bump115 may be configured on the surface of the first substrate 11corresponding to the MEMS element 124 to reduce the contacting area ofthe MEMS element 124 and the first substrate 11 and prevent failurecaused by sticking between the MEMS element 124 and the first substrate11.

In the embodiment shown in FIG. 3, the micro channel 117 is configuredon the side of the first substrate 11, which forms a trench on thesurface of the first substrate 11 and then mounts the first substrate 11and the second substrate 12 to form the micro channel 117. In onepreferred embodiment, referring to FIG. 5, the micro channel 117 may bealso configured on the side of the second substrate 12, which forms atrench on the first surface 121 of the second substrate 12 and thenconnects the first substrate 11 and the second substrate 12 to form themicro channel 117.

Refer to FIG. 7, which is a partial schematic diagram showing thestructure of the micro channel of the unconnected second substrate 12.In the embodiment shown in FIG. 7, the micro channel 117 comprises abent portion 117 a bending to horizontal direction (along the interfacebetween the first substrate and the second substrate). Therefore, whenforming the first airtight ring 123 a, material of the first airtightring 123 a will heap up in the bent portion 117 a without contaminatingthe chamber 126. It may be understood that the same function may be alsoperformed by the micro channel 117 having a bent portion bending tovertical direction (vertical to the first surface of the secondsubstrate).

Referring to FIG. 8, in one preferred embodiment, at least one dam 117 bmay be configured in the micro channel 117. The dam 117 b may reduce theinner diameter of the micro channel 117 to allow the anti-stickingmaterial to may pass through such that the material of the firstairtight ring 123 a would heap up in the dam 117 b without contaminatingthe chamber 126. In another preferred embodiment, referring to FIG. 9,the dam 117 b can also reduce the inner diameter of the micro channel117 on vertical direction and only the above portion of the microchannel 117 can be passed through, so that the filler may be blocked infront of or within the dam 117 b by the dam 117 b.

In the embodiment shown in FIG. 1, a notch is formed on side of thefirst surface 121 of the second substrate 12 for thinning the MEMSelement 124. The notch 124 a may be also formed on side of the secondsurface 122 of the second substrate 12 for thinning the MEMS element124, as shown in FIG. 6. In one preferred embodiment, a notch 125 a maybe also formed on side of the second surface 122 of the second substrate12 for thinning the reference element 125. It should be understood that,for avoid the thinned reference element 125 deforming with the outsidepressure difference, a channel 125 b may be configured to connect thechamber 127 which is defined by the reference element 125 and then thereis no pressure difference between the chamber 127 and the outsideenvironment. Hence, the reference element 125 will not have deformationcaused by the outside pressure difference.

Refer to FIGS. 10a to 10g , which are cross-sectional diagrams showingthe manufacture steps of the pressure sensor of a preferred embodimentof the present invention. First, a first substrate 11 comprising adriving circuit and/or a detecting circuit is provided. The analogand/or digital circuits may be used in the first substrate 11, and aregenerally practiced by using application-specific integrated circuit(ASIC) designed devices. The first substrate 11 may be also named theelectrode substrate. In one preferred embodiment of the presentinvention, the first substrate 11 may be any substrate with suitablemechanic stiffness, such as complementary metal oxide semiconductor(CMOS) substrate or glass substrate. Only one chip is shown in thecross-sectional figures, however, it is understood, a plurality of chipsmay be formed on one substrate simultaneously. It is only used forexplaining the present invention with single device, not for limitingthe manufacture method. In the following specification, a completeexplanation of the wafer level process applied to a substrate tomanufacture a plurality of chips or devices will be described. After thedevices are manufactured, the dicing and singulation technologies may beapplied to produce the single-device package to fit all applications.

Referring to FIG. 10a , a first dielectric layer 112 a with apredetermined thickness is configured on the first substrate 11. In onepreferred embodiment, the first dielectric layer 112 a may be a SiO₂layer; however, other suitable materials may be used in the presentinvention as well and are also in the scope of the present invention.For example, in another embodiment, Si₃N₄ or SiON may be deposited toform the first dielectric layer 112 a. In a further embodiment, apolysilicon material, including the amorphous polysilicon, may bedeposited to form the first dielectric layer 112 a. Any material withappropriate characteristic, including mighty connection to thesubstrate, great adherence to the first substrate 11, and suitablemechanic stiffness, may be used to replace the Si_(x)O_(y) material. Insome specific applications, a buffer layer may be used in the depositionprocess of the first dielectric layer 112 a.

In some embodiments, the first dielectric layer 112 a is formed bymultiple deposition and polishing processes. For example, the firstportion of the first dielectric layer 112 a may be formed by using thehigh-density plasma (HDP) deposition process, and then using thechemical mechanical planarization (CMP) process to polish. The densityof the device feature is a variable, and it may be a relative horizontalposition difference, that is the deposition layer probably has an unevenupper surface. Hence, the multiple deposition and polishing processesmay form an evener and flatter surface. The example of the depositiontechnology includes Tetraethyl Orthosilicate (TEOS), High-Density Plasma(HDP), Chemical Vapor Deposition (CVD), Low Pressure Chemical VaporDeposition (LPCVD) and Thermal Oxidation. Besides, other materials maybe also applied when a final layer (such as an oxide) is covered on.

In some embodiments, the deposition of the first dielectric layer 112 ais processed according to the structure of the substrate. For example,when the first substrate 11 is a complementary metal oxide semiconductor(CMOS) substrate, the high temperature deposition process may damage themetal layer or cause the diffusion effect on the contacting surface ofthe circuits, and some circuits on the substrate may be affected.Therefore, in one specific embodiment of the present invention, the lowtemperature deposition, patterning and etching processes, such asprocesses in temperature lower than 500° C., are used to form the layersshown in FIGS. 10a to 10g . In another specific embodiment of thepresent invention, the deposition, patterning and etching processes areperformed in the temperature lower than 450° C. to form layers shown infigures. After the first dielectric layer 112 a is formed, it may befurther patterned and etched to form multiple first interconnect via 118a. The first interconnect via 118 a provides the electrical connectionbetween the first substrate 11 and the first metal layer 111 a laterformed on the first dielectric layer 112 a, and this process will befurther explained below.

Then, a first metal layer 111 a is formed above the first dielectriclayer 112 a. The first metal layer 111 a fills in the first interconnectvia 118 a. In some embodiments, the first interconnect via 118 a may befilled by a conductive material (such as tungsten). In one preferredembodiment, the first metal layer 111 a is deposited by using plating,Physical Vapor Deposition (PVD) or Chemical Vapor Deposition (CVD)processes. FIG. 10a shows the first substrate 11 and the patterned firstmetal layer 111 a after the etching process. For explaining the presentinvention in a more specific way, a lithography process is not shown inthe manufacture process, wherein a photoresist layer is deposited on thefirst metal layer 111 a and then is patterned to form an etching mask.In the lithography process, the size of the etching mask may be strictlycontrolled, and may be performed by using any suitable materialresistant to the etching process while etching the metal layer. In onespecific embodiment, the Si₃N₄ is used as the etching mask. Although anone-dimensional cross-sectional diagram is shown in FIG. 10a , it shouldbe understood, however, a predetermined two-dimensional pattern isformed on the metal layer. In one embodiment, the first metal layer 111a comprises aluminum, copper, aluminum-copper-silicon alloy, tungstenand titanium nitride.

Then, a second dielectric layer 112 b is formed above the first metallayer 111 a. In some preferred embodiments, the process and material toform the second dielectric layer 112 b is similar to the process offorming the first dielectric layer 112 a. In other embodiments, theprocess and material to form the second dielectric layer 112 b isdifferent from the process of forming the first dielectric layer 112 a.In other embodiments, the process and material to form the seconddielectric layer 112 b may be partially similar to and partiallydifferent from the process of forming the first dielectric layer 112 a.After the second dielectric layer 112 b is formed, it will then bepatterned and etched to form multiple second interconnect via 118 b. Thesecond interconnect via 118 b provides the electrical connection betweenthe first metal layer 111 a and the second metal layer 111 b laterformed on the second dielectric layer 112 b, and this process will beexplained more below. It should be noted here that, in addition to usageas the conductive path between the first metal layer 111 a and thesecond metal layer 111 b, the second interconnect via 118 b may be usedto form the second airtight ring 118 c as well.

Then, a second metal layer 111 b is formed above the second dielectriclayer 112 b. The second metal layer 111 b fills into the secondinterconnect via 118 b. In some embodiments, the second interconnect via118 b may be filled with a conductive material (such as tungsten). Thepatterned second metal layer 111 b may be used as the electrode of theMEMS device, such as the first circuit 113 a and the second circuit 113b used as detecting and/or driving circuits, the conductive contact 113c electrically connected to the second substrate 12, or the contactregion 113 d connecting to the third substrate 13. The contact region113 d comprises a conductive material having sufficient mechanicstiffness to support the connection interface. In one specificembodiment, the contact region 113 d and the first substrate 11 form alow resistance ohmic contact. In some embodiments, the contact region113 d comprises germanium, aluminum or copper. In other embodiments,other materials may be used as the contact region 113 d, such as gold,indium, or other solder capable of bottom-mounting and moistly improvingmetal stack.

Referring to FIG. 10b , a third dielectric layer 112 c is formed abovethe second dielectric layer 112 b. The process and material to form thethird dielectric layer 112 c is similar to the process of forming thesecond dielectric layer 112 b shown in FIG. 10a . Then, the thirddielectric layer 112 c is patterned to expose the first circuit 113 a,the second circuit 113 b, the conductive contact 113 c and the contactregion 113 d of the second metal layer 111 b. The etching processcomprises one or more than one etching steps, such as anisotropicetching, oxide etching, wet etching or dry etching, for example ReactiveIon Etching (RIE). In one preferred embodiment, the etching process maydefine one or multiple mechanic anti-moving structures of the MEMSdevices, such as the anti-moving bump 116 shown in FIG. 10b . In onepreferred embodiment, one or multiple buffer layers may be used asetching stop layer. For example, the metal layer 114 of the first metallayer 111 a can prevent the exposure of the first dielectric layer 112a. The person with ordinary skill in the art should understand thechange, modify or replace of the embodiments is still in the scope ofthe present invention. In one preferred embodiment, the etching processcan also define multiple fences 117. The fences 117 are configuredsurrounding the contact region 113 d to prevent migrating of metal inthe connection process and failing of the device. In one preferredembodiment, for manufacturing the pressure sensor shown in FIG. 3, atleast one trench may be formed on the third dielectric layer 112 c, andafter mounting the second substrate 12 and the first substrate 11, thetrench on the first substrate 11 can form the micro channel 17 as shownin FIG. 3.

Referring to FIG. 10c , a second substrate 12 is provided and a notch124 a is formed on the first surface 121 of the second substrate 12.When the second substrate 12 and the first substrate 11 are connected,the notch 124 a can help to reduce the interference from the firstsubstrate 11. It should be understood that the notch may be also formedon the position corresponding to the reference element 125, and thefinal thickness of the reference element 125 has to be thicker than thatof the MEMS device 124, or a suitable channel has to be formed to avoidthe deformation of the reference element 125. It should be noted thatthis step may be also omitted when the embodiment shown in FIG. 6 ismanufactured, and the notch 124 a will be formed on the second surface122 of the second substrate 12 in the later steps. Further, formanufacturing the embodiment shown in FIG. 5, the trench correspondingto the micro channel 115 has to be formed on the first surface 121 ofthe second substrate 12 in this step.

Referring to FIG. 10d , the first surface 121 of the second substrate 12faces to the first substrate 11 and is mounted to the first substrate11. The mounting of the second substrate 12 and the first substrate 11may be achieved by using one of the methods of fusion bond, eutecticbonding, conductive eutectic bonding, soldering and bonding. In someembodiments, the Anisotropic Conductive Film (ACF) may be used to bondthe second substrate 12 to the first substrate 11. After the secondsubstrate 12 and the first substrate 11 are connected, a first chamber126 and a second chamber 127 are defined, wherein the first circuit 113a is configured in the first chamber 126, and the second circuit 113 bis configured in the second chamber 127.

Then, the second substrate 12 is thinned to a predefined thickness byperforming a grinding and/or other thinning procedures to the secondsubstrate 12. As shown in FIG. 10e , in some embodiments, the remainthickness of the thinned region corresponding to the MEMS device 124 isabout 10 μm to 100 μm, and the MEMS device 124 may be deformed with thepressure difference. The predefined thickness may be achieved by usingthe traditional thinning technology, such as chemical mechanicalplanarization (CMP), wet etching and/or dry etching, for exampleReactive Ion Etching (RIE) technologies. There is no stopping layer toend the thinning process in the embodiment shown in FIG. 10d , and thethinning process adopts an exact control. The thickness of the secondsubstrate 12 may be thinner or thicker than the predefined thickness inthe absence of exact control during the thinning process, and theperformance of the manufactured MEMS device will be thus affected. Inother embodiments, an etching stopping layer is integrated into thesecond substrate 12 for the exact control of the thinning process. Theperson with ordinary skill in the art should understand the change,modify or replace of the embodiments is still in the scope of thepresent invention.

Referring to FIG. 10e , the second substrate 12 is patterned and etchedto form a through slot 128 a and a via 128 b. The through slot 128 a andthe via 128 b penetrate the first surface 121 and the second surface 122of the second substrate 12. The through slot 128 a expose the secondmetal layer 111 b of the first substrate 11 to make the later-formedfirst airtight ring 123 a connecting to the second metal layer 111 b ofthe first substrate 11. The via 128 b corresponds to the conductivecontact 113 c to expose the conductive contact 113 c. It should beunderstood that, for manufacturing the embodiment shown in FIG. 3, thethrough slot 128 a formed in this step may be connected to the microchannel 117 to achieve the connection of the first chamber 126 to theoutside environment through the through slot 128 a and the micro channel117, and then the anti-sticking material may be introduced to the firstchamber 126 and form an anti-sticking layer on the inner surface of thefirst chamber 126.

Referring to FIG. 10f , then, filler is filled into the through slot 128a to form the first airtight ring 123 a. A conductive material (such astungsten) is stuffed into the via 128 b to make the via 128 b be aconductive via 123 b and electrically connect the second substrate 12and the conductive contact 113 c of the first substrate 11. In onepreferred embodiment, the filler filled in the through slot 128 a may bethe same as that in the via 128 b. As described above, the forming andfilling steps of the through slot 128 a and the via 128 b may befinished together with same process. Therefore, there is no extraprocess step needed to form the first airtight ring 123 a, and theprocess is essentially simplified. It should be noted here that theforming and filling steps of the through slot 128 a and the via 128 bmay be also finished according to the actual requirement and withsuitable processes respectively. It should be understood that, formanufacturing the embodiment shown in FIG. 3, the step of filling thethrough slot 128 a seals the micro channel 117 simultaneously to retainthe airtightness of the first chamber 126 without extra process.

Referring to FIG. 10g , a third substrate 13 is provided. In someembodiments, the third substrate 13 comprises doped silicon, ceramicwith a conductive coating, glass covered by a conductive coating (suchas ITO), or metal layer like Tantalum oxide. A sticking layer is placedon the surface of the third substrate 13. The sticking layer can assistthe mounting between the third substrate 13 and the first substrate 11.In some embodiments, the sticking layer is formed by depositing a seedlayer, such as titanium/gold, and then depositing a conductive layer(such as plating gold). Then, the third substrate 12 is patterned andetched to form a plurality of bracket structure 131. The third substrate13 is etched to form the bracket structure 131, and a notch region 132is formed on the third substrate 13. The partial sticking layer isremained on the bracket structure 131 to form the contact pad 133. Thenotch region 132 may be configured surrounding the second substrate 12.The horizontal size of the notch region 132 is selected according to thegeometric structure of the second substrate 112 covered by the thirdsubstrate 13. In one embodiment, in the process of forming the bracketstructure 131, one or multiple trenches may be formed at the terminal ofthe bracket structure 131. When the third substrate 13 is connected tothe first substrate 11 through the bracket structure 131, the trenchesmay be used as the channel 134 connecting the notch region 132 and theoutside, as shown in FIG. 1. The connection step of the third substrate13 and the first substrate 11 may be achieved by using one of themethods of fusion bond, glass frit bonding, eutectic bonding, conductiveeutectic bonding, soldering and bonding. In some embodiments, the MEMSdevice 124 is protected by using a lower adopted temperature forconnecting the third substrate 13 and the first substrate 11 than theadopted temperature for connecting the second substrate 12 and the firstsubstrate 11 to. The third substrate 13 is conductive and can shield theelectromagnetic disturbance (EMI) of the second substrate 12. It shouldbe noted that the third substrate 13 is an optional device, that is, thepressure sensor of the present invention may be function as well in thecase of absence of the third substrate 13.

To sum up the foregoing descriptions, the pressure sensor using the MEMSdevice and the manufacture method thereof are achieved by using anairtight ring surrounding a chamber defined by the first substrate andthe second substrate. The airtight ring extends from the upper surfaceof the second substrate to the interface between the first substrate andthe second substrate and further protruding from the interface. Hence,the airtight ring is capable of blocking extension of the chamber to theinterface between the first substrate and the second substrate,preventing the air leakage from the surface between the first substrateand the second substrate, and therefore retaining the airtightness ofthe chamber.

While the invention may be subject to various modifications andalternative forms, a specific example thereof has been shown in thedrawings and is herein described in detail. It should be understood,however, that the invention is not to be limited to the particular formdisclosed, but on the contrary, the invention is to cover allmodifications, equivalents, and alternatives falling within the spiritand scope of the appended claims.

What is claimed is:
 1. A pressure sensor, comprising: a first substratecomprising a metal layer, wherein the metal layer is partially exposedon a surface of the first substrate to form a first circuit, a secondcircuit and a conductive contact; and a second substrate comprising afirst surface and a second surface, wherein the second substrate facesthe surface of the first substrate with the first surface and iselectrically connected to the conductive contact, wherein the secondsubstrate comprises: a MEMS element corresponding to the first circuitand defining an airtight chamber with the first substrate and the secondsubstrate; a reference element corresponding to the second circuit andkept a fixed distance from the second circuit; and a first airtight ringconfigured for surrounding the chamber, wherein the first airtight ringpenetrates the second surface of the second substrate, extends to aninterface between the first substrate and the second substrate, andprotrudes from and breaks out the interface.
 2. The pressure sensoraccording to claim 1, wherein the first airtight ring connects to themetal layer of the first substrate.
 3. The pressure sensor according toclaim 1, wherein the first airtight ring comprises a conductivematerial.
 4. The pressure sensor according to claim 1, furthercomprising: a second airtight ring corresponding to the first airtightring, configured on the first substrate and connecting the metal layerand another lower metal layer.
 5. The pressure sensor according to claim1, further comprising: an anti-sticking layer configured on the innersurface of the chamber, wherein the chamber comprises at least one microchannel extending to the first airtight ring, and the micro channel isconfigured on the first substrate or the second substrate.
 6. Thepressure sensor according to claim 5, wherein the micro channelcomprises a bent portion bending to horizontal or vertical direction. 7.The pressure sensor according to claim 5, wherein the micro channelcomprises a dam for reducing the inner diameter of the micro channel. 8.The pressure sensor according to claim 1, wherein the MEMS elementcomprises a notch configured on side of the first surface or side of thesecond surface.
 9. The pressure sensor according to claim 1, wherein ananti-moving bump is configured on the surface of the first substratecorresponding to the MEMS element.
 10. The pressure sensor according toclaim 1, wherein the second substrate comprises a conductive viapenetrating the first surface and the second surface of the secondsubstrate, wherein the conductive via is electrically connected to theconductive contact and the second substrate through an ohmic contact,and the ohmic contact region is made of at least one of silicon,aluminum-copper alloy, titanium nitride and tungsten.
 11. The pressuresensor according to claim 10, wherein the conductive via is integratedinto the first airtight ring.
 12. The pressure sensor according to claim1, wherein the first substrate comprises a complementary metal oxidesemiconductor substrate.
 13. The pressure sensor according to claim 1,further comprising: a third substrate having a notch region and aplurality of bracket structure, the third substrate is configured abovethe second substrate and is connected to the first substrate through thebracket structure to place the second substrate in the notch region. 14.The pressure sensor according to claim 13, wherein the third substratecomprises a channel configured on a terminal of the bracket structure.